This disclosure relates to efficiently focusing light.
By tracking the motion of a pen, for example, as it is used to write or draw on paper, it is possible to capture and reproduce electronically what is being written or drawn. Motion of a stylus that does not leave a mark on a writing surface can also be tracked. Systems for accomplishing this were described in U.S. Patent application Ser. No. 10/623,284 (Now U.S. Pat. no. 7,268,774), filed Jul. 17, 2003, which is incorporated here by reference.
In some proposed approaches, the surface on which the pen is moving may have an array of pixels or other sensing locations, such as touch sensors, each of which responds when the pen is at such a location. In other techniques triangulation algorithms are used to track the motion.
As described in the above-referenced application, the pen may emit light that is detected by sensors mounted on the writing surface, and its position may be determined based on the readings of those sensors.